EP3561385A1 - Refractory wall with anti-corrosive layer - Google Patents

Abstract

A refractory wall (W), in particular for a combustion furnace, comprises a, in particular metallic, base element (1) and a refractory protective covering (2) made of refractory plates (21) which is placed in front of the base element (1). For protection against flue gases passing through the protective lining (2), the base element (1) has a ceramic corrosion protection layer (10) at least on one side facing the protective lining (2).

Description

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

Such refractory walls are used for example in combustion chambers of combustion plants for the recovery of heat energy of the hot flue gases. In principle, a distinction must be made between walls which form part of the boundary walls of a combustion furnace in practical use, and walls which, for example, are suspended in practical use inside the incinerator and are exposed to flue gas on several sides. Typical representatives of such walls are eg in the CH 699 406 A2 respectively. WO 2016/109903 A1 described.

The usually metallic base element of the wall is often formed as a tube wall and is usually made of webs connected by pipes. The refractory protective lining is pre-set to the pipe wall and is intended to protect the pipe wall from corrosion by flue gases. The refractory protective lining is usually formed in rows and columns side by side or superimposed plates. Depending on the intended use, the protective cover is only arranged on one side of the pipe wall (eg CH 699 406 A2 ) or the protective cover encloses the pipe wall all around (eg WO 2016/109903 A1 ).

Protective cover protected base elements are used e.g. Also used in fluidized bed ovens, where it comes to protect a metallic boiler wall from corrosion by flue gases. In this case, the base member is formed by the boiler wall.

The panels of the protective cover are usually mutually sealed by various measures to some extent to prevent the passage of flue gases. However, in practice this alone can not completely avoid that corrosive flue gases through the protective lining reach and the underlying base element, so for example, the pipe wall or boiler wall attack.

So-called actively ventilated systems address this problem by the fact that through the space between the base member and the distance superior protective shielding a protective gas - in general air - is pumped through. The gas or air is in this case with respect to the combustion chamber of the combustion furnace under a slight overpressure, which prevents the flue gases from penetrating from the combustion chamber into the wall space and can attack the metallic base element. Typical examples of such ventilated systems are eg in CH 699 406 A2 respectively. WO 2016/109903 A1 as well as in the EP 2 754 961 A2 described.

Active ventilated systems are structurally relatively complex because of the required protective gas supply. In addition, energy is consumed for pumping the protective gas under pressure.

By the present invention, therefore, a refractory wall to be improved so that on the one hand can be dispensed with an active ventilation and on the other hand, a reliable protection of at least one base element is achieved against the corrosive effect of flue gases.

This object of the invention is achieved by the inventive refractory wall, as defined in independent claim 1. Claim 15 defines a method for producing such a refractory wall. Particularly advantageous developments and refinements of the invention will become apparent 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 lining of refractory plates which is pre-fitted to the at least one base element. The at least one base element has a ceramic corrosion protection layer at least on one side facing the protective lining. Due to the ceramic corrosion protection layer, aggressive flue gases which have penetrated through the protective lining can not attack the at least one base element, so that an 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 covering entirely or only in regions, for example, if another corrosion protection is provided for certain areas or none at all is required.

Preferably, the ceramic corrosion protection layer has a content of tricalcium aluminate and SiC which is at least 60% by weight. Thus, a high temperature resistance and protective effect can be achieved.

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

Preferably, the ceramic paste is a mixture of solid components and water and immediately after mixing its constituents, based on the totality of its solid constituents, contains 20-80% by weight, preferably 35-75% by weight, SiC and additionally one portion from 10-50 wt.% Al ₂ O ₃ , 5-30 wt.% SiO ₂ and 1-5 wt.% CaO. With these compositions, on the one hand, a high temperature resistance and protective effect can be achieved and, on the other hand, the thermal expansion coefficient can be adapted to that of the at least one base element so that the corrosion protection layer reliably adheres to the at least one base element under thermal stress. Advantageously, the coefficient of thermal expansion of the anticorrosive layer differs by no more than 10% from the thermal expansion coefficient of the at least one base element.

Advantageously, the anticorrosion layer 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 optimum heat transfer.

The at least one base element is preferably metallic.

Conveniently, the at least one base element comprises pipes for the passage of a fluid medium.

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

Advantageously, the refractory protective lining is arranged at a distance from the at least one base element, wherein a gap is present between the at least one base element and the protective lining. Flue gases that have penetrated through the protective cover can escape through this intermediate space.

Conveniently, the refractory plates are attached via at least one plate holder on at least one base element.

Preferably, the refractory plates of the protective cover are arranged in rows and columns next to and above each other. Such an arrangement facilitates the assembly of the protective cover and also the replacement of defective plates.

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

In an advantageous embodiment, 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 is as follows: 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 brushed or sprayed, and the ceramic paste is then brought to hardening or setting. The at least one base element is pre-set after the application of the ceramic paste, a refractory protective cover made of refractory plates.

The application of a ceramic paste is much easier and cheaper than e.g. the welding of protective alloys.

The embodiments and advantages mentioned with regard to the refractory wall according to the invention also apply correspondingly 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.

In the following the invention will be described in more detail with reference to exemplary embodiments illustrated in the drawings. Show it:

Fig. 1

- A section of a first embodiment of an inventive refractory wall in supervision;

Fig. 2

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

Fig. 3

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

Fig. 4

- an enlarged detail from Fig. 3 ;

Fig. 5

- A section of a second embodiment of an inventive refractory wall in supervision;

Fig. 6

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

Fig. 7

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

Fig. 8

- an enlarged detail from Fig. 7 ,

The following definition applies to the following description: If reference signs have been given in a figure for the purpose of clarity of drawing, but are not mentioned in the directly related part of the description, reference is made to their explanation in the preceding or following parts of the description. Conversely, less relevant reference numerals are not included in all figures to avoid overcharging graphic for the immediate understanding. For this purpose, reference is made to the other figures.

Location and direction designations, such as top, bottom, side by side, one above the other, side, vertical, horizontal, height and width refer to the usual vertical insert position of the refractory wall shown in the drawings.

As a basic element in the context of the invention, any type of, in particular metallic, construction understood. In particular, this may be a metallic vessel wall or an array of (e.g., parallel) tubes through which a fluid medium (e.g., water) is permeable. The basic element is in particular also a pipe wall consisting of several interconnected pipes or a single pipe.

That in the Figures 1-4 illustrated first embodiment of an inventive refractory wall is in practical use a part of a Boundary wall of a combustion furnace, with its protective lining is aligned with the interior of the incinerator. The wall is acted upon by one side of hot flue gases.

The designated as a whole with W refractory wall comprises a metal tube wall 1 designed as a base element and a refractory protective cover 2, which is the pipe wall 1 is set at a distance, so that between the protective cover 2 and the pipe wall 1 is a gap 3 ( Figures 2 and 4 ), through which air can flow.

The tube wall 1 forming the base element consists of a multiplicity of vertical tubes 11 which are used in practice and which are held together by webs 12 at a mutual distance (see in particular FIG Fig. 4 ). The tubes 11 and the webs 12 are usually made of steel.

The protective covering 2 consists of a plurality of juxtaposed and superimposed refractory plates 21 arranged in rows and columns. The plates are, for example, ceramic SiC plates, preferably SiC 90 plates having an SiC content of about 90% by weight in the production that are fire resistant up to over 1000 ° C.

The plates 21 of the protective cover 2 are fixed to the tube wall 1 by means of plate holders 13. The plate holders 13 are made of heat-resistant steel, for example steel No. 310 according to AISI standard or material No. 1.4845 according to DIN 17440. Also suitable are corrosion-resistant CrNi alloys, in particular with additives such as molybdenum. The plate mounts 13 essentially comprise in each case one bolt which is welded to a web 12 and one nut which is seated on the bolt. The plate holders 13 engage in vertically continuous, inwardly widened grooves 21a (FIG. Fig. 4 ) of the plates 21 and set the distance of the plates 21 to the pipe wall 1 firmly. The plate brackets 13 also serve to support the plates 21 in the vertical direction, the plates 21 with arranged on them (not shown) bridge elements rest on the plate brackets 13. The plates 21 are in the vertical direction in movable to a certain extent so as to allow thermally induced expansion or contraction movements.

Between the juxtaposed plates 21 extend vertical joints 23 and between the superposed plates 21 are horizontal joints 24. The joints are sealed in a conventional manner by inserted sealing elements and / or an overlapping formation of the plate edges (not shown in detail).

As far as corresponds to the inventive refractory wall in their basic structure and in their operation conventional walls of this type, as for example in the CH 699 406 A2 . WO 2016/086322 A1 and WO 2016/109904 A1 in detail, in particular also with regard to the design of the refractory plates are described. The expert therefore needs so far no further explanation.

The essential difference of the inventive refractory wall over 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 is best described in detail. FIG. 4 recognizable. The anticorrosive layer 10 prevents smoke leaks that have penetrated the pipe wall 1 due to leaks in the protective covering 2 into the intermediate space 3 between the protective covering 2 and the pipe wall 1. As a result, a structurally complex active ventilation (pumping through a gas, eg air, under pressure through the gap 3 of the wall) can be omitted. The penetrated flue gases can be removed through the gap 3.

The ceramic corrosion protection layer 10 covers here the entire tube wall 1 including the webs 12 between the individual tubes 11. It consists of a hardened or (hydraulically) hardened ceramic paste, which consists of a mixture of different solid constituents and water. Immediately after the mixing of its solid constituents and before the addition of water, the paste contains as the essential constituent 20-80%, preferably 35-75%, SiC. Further constituents at this time are 10-50% Al ₂ O ₃ , 5-30% SiO ₂ and as binder 1-5% CaO. The proportions of these solid components (excluding water) are always chosen to complement each other to 100%. Thereafter, about 6% water (H ₂ O) is added (resulting in a total amount of about 106%), whereby a pasty-liquid state of matter is achieved. All percentages are by weight.

SiO ₂ , Al ₂ O ₃ and CaO react together with H ₂ O, whereby H ₂ O is degraded to a large extent (chemically bonded). The rest of the H ₂ O evaporates at the latest during operation. The SiC reacts only minimally. Among other things, the SiO ₂ contributes to the strength of the corrosion protection layer. During hydration (setting), so-called calcium silicate hydrate fibers (Ca ₃ S ₂ H ₃ ) are formed, which combine with the three constituents SiO ₂ , Al ₂ O ₃ and CaO to form the hardened product "tricalcium aluminate". The SiC is merely an aggregate, which is embedded by the tricalcium aluminate and solidifies after setting to the actual ceramic mortar. After setting, a ceramic corrosion protection layer is present in which the proportion of tricalcium aluminate and SiC is at least 60% by weight.

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

The grain size of the SiC in the ceramic paste is preferably <2 mm, more preferably <1 mm. The thickness of the anticorrosion 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 corrosion protection layer 10 is painted or sprayed onto the pipe wall 1 as a paste in the production of the wall and then hardens or hydraulically binds. Usually, paste is mixed together and then within 5 min. applied up to 1 hour. After that it is already hardened so far that it can hardly be applied anymore.

The composition of the ceramic paste is further selected so that the corrosion protection layer in the cured or hardened state has a similar as possible (at most 10% different) thermal expansion coefficient as the pipe wall or generally the base element. The composition of the paste can advantageously be based on the expected temperature range, which reaches the base element (in this case the metallic pipe wall 1) in use. At higher expected temperatures of the base element, the SiC content is reduced and the (highly heat-resistant) Al ₂ O ₃ content increased, as the table below 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 25 1 1 6 280 ° C 60 10 22 1 1 6 260 ° C 63 10 19 1 1 6

In the examples of the above table, the paste additionally contains a small amount of Fe ₂ O ₃ , which promotes nitride formation and thereby curing. However, this proportion is not absolutely necessary and can therefore be omitted.

That in the Figures 5-8 illustrated second embodiment of the novel refractory wall is intended, in practical use be arranged as a heat exchanger inside a combustion furnace, wherein the wall is acted on several sides by hot flue gases. It is basically similar in structure to the refractory wall of the Figures 1-4 , but with the difference that their base element, so the pipe wall, is protected on four sides or all around by a refractory protective cover.

The refractory wall again comprises a base element formed as a metallic tube wall 1 and a refractory protective covering 20, which is set at four sides at a distance from the tube wall 1, so that there is a gap 3 between the protective covering 20 and the tube wall 1 ( FIGS. 6 and 8th ).

The tube wall 1 forming the base element again comprises a multiplicity of vertical tubes 11 which are used in practice and which are held together by webs 12 at a mutual distance (see in particular FIG Fig. 8 ).

The protective cover 20 is analogous to the in the Figures 1-4 illustrated embodiment of a plurality of side by side and one above the other, arranged in rows and columns refractory plates 21 and 22 which are fixed to the pipe wall 1 by means of plate holders 13. In contrast to the first embodiment encloses in this embodiment, the protective cover 20, the pipe wall 1 completely around. At the two opposite longitudinal sides of the tube wall 1, substantially flat plates 21 are arranged as in the first embodiment and in addition are arranged along the lateral end edges of the tube wall 1 in cross-section substantially U-shaped plates 22 which surround the lateral end edges of the tube wall 1, so the protective covering 20 forms a closed envelope around the pipe wall 1, whereby a gap 3 remains between the pipe wall and the protective covering 20 around the pipe wall 1. The plates 22 are also fastened to the tube wall 1 by means of plate holders 13, these plate holders being made into vertically continuous, inwardly widened grooves 22a (FIG. Fig. 8 ) of the plates 22 engage.

So far, this embodiment corresponds to a novel wall in its basic structure and in its operation, for example, in the WO 2016/109903 A1 described conventional wall. With regard to the design of the refractory plates and the plate mounts, what has been said in connection with the first embodiment applies. The expert therefore needs with respect to the second embodiment so far no further explanation.

The essential difference of the inventive refractory wall over conventional refractory walls of this type is also in this second embodiment is that the tube wall 1 or generally the base member is coated with a ceramic corrosion protection layer 10, which prevents from leaks in the protective cover 20 in the space 3 between the protective cover 20 and the pipe wall 1 penetrated flue gas can attack the pipe wall 1. The corrosion protection layer 10 is best described in detail. FIG. 8 recognizable. With regard to the anticorrosion layer 10 and its underlying ceramic paste is again explained in connection with the first embodiment.

The at least one base element can also comprise an arrangement of two or more pipes which are not connected by webs, the pipes being coated again with the already mentioned ceramic corrosion protection layer. Metallic base elements consisting of unconnected pipes (without anticorrosion layer) are, for example, in EP 2 754 961 A2 described.

The at least one base element may also be formed by a metallic boiler wall, this boiler wall, the protective cover is set at a distance. In this case, the boiler wall has a ceramic corrosion protection layer only on its side facing the protective covering.

Claims (15)

Refractory wall (W), in particular for a combustion furnace, comprising at least one base element (1) and a refractory protective lining (2; 20) made of refractory plates (21, 22) provided in front of the at least one base element (1), characterized in that the at least a base element (1) has a ceramic corrosion protection layer (10) at least on one side facing the protective lining (2; 20). Refractory wall (W) according to claim 1, characterized in that the ceramic corrosion protection layer (10) has a content of tricalcium aluminate and SiC which is at least 60 wt.%. Refractory wall (W) according to claim 1 or 2, characterized in that the corrosion protection layer (10) is a hydraulically hardened ceramic paste. Refractory wall (W) according to claim 3, characterized in that the paste is a mixture of solid constituents and water and, immediately after the mixing of its constituents based on the totality of its solid constituents, a proportion of 20-80% by weight, preferably 35-80% by weight. 75 wt.% Contains SiC. Refractory wall (W) according to claim 4, characterized in that the paste immediately after mixing its constituents based on the totality of their solid constituents, a proportion of 10-50 wt.% Al ₂ O ₃ , 5-30 wt.% SiO ₂ and 1-5 wt% CaO. 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. 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 more than 10% of the thermal expansion coefficient of the at least one base element (1). Refractory wall (W) according to one of the preceding claims, characterized in that the at least one base element (1) is metallic. 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. Refractory wall according to one of the preceding claims, characterized in that the at least one base element (1) is designed as a tube wall with tubes (11) connected by webs (12). Refractory wall (W) according to one of the preceding claims, characterized in that the refractory protective covering (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 covering (2; 20) a gap (3) is present. 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). Refractory wall according to one of the preceding claims, characterized in that the protective covering (20) surrounds the at least one base element (1) all around. Refractory wall (W) according to one of the preceding claims, characterized in that the at least one base element (1) is a boiler wall. Method for producing a refractory wall (W) according to one of the preceding claims, characterized in that by mixing solid Ingredients and water, a hydraulically setting ceramic paste is prepared, that this paste as a corrosion protection layer on the at least one base element (1) applied, in particular brushed or sprayed, and is then brought to curing, and that the at least one base element (1) after the Applying the ceramic paste, a refractory protective cover (2, 20) made of refractory plates (21, 22) is provided.

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